The invention relates generally to peristaltic pumps and more specifically to a peristaltic cartridge pump for pumping fluid through a plurality of lengths of tubing.
Peristaltic pumps are preferred for certain applications due to their ability to pump fluids through tubing without any contact between pump components and the fluid being pumped. In a typical peristaltic pump system, one or more lengths of tubing are contacted by a series of rollers that generally rotate in a circular path. The peristaltic pump may be rotated by a variable-speed electric motor or other suitable drive.
Peristaltic pumps with removable cartridges are employed to pump fluid through a plurality of flexible lengths of tubing simultaneously. The removability of the cartridges is advantageous in that it enables a particular length of tubing to be removed or replaced without disturbance of other lengths of tubing in the pump. U.S. Pat. No. 4,886,431, the disclosure of which is incorporated by reference, illustrates and describes a cartridge pump which has proven to be well-suited for many laboratory applications and the like, particularly those wherein the capability for fine-tuning of the degree of occlusion is useful.
Cartridge pumps generally draw discrete volumes of fluid through the tubing by positively displacing them rotationally between the contact points of two rollers of the pump and the occlusion surface of the cartridge as the rollers rotate around the drive unit rotor. The expulsion of these discrete volumes of fluid results in pulsed flow in the output tubing. As a roller passes the end of the occlusion bed, a segment of tubing that had been pressed flat by the tubing expands, and the downstream flow velocity decreases and/or reverses direction for a brief interval. In some applications, such as liquid chromatography, the pulsating flow may cause undesirable results. In other applications, flow pulsation is not undesirable per se, but precise synchronization of flow through a plurality of parallel conduits is desired.
One suggestion for reducing pulsation in peristaltic pump outflow, set forth in U.S. Pat. No. 4,834,630, is to provide a segmented rotor having rollers in a first segment staggered or alternated with respect to rollers in a second segment, with each segment engaging a plurality of fluid conduits, and with each fluid conduit engaged by the first segment connected by a T-shaped coupler to one engaged by the second segment on the output side of the pump. Another approach which has been proposed is to employ twin tubes engaged by a pair of offset, spring-loaded tracks in a single peristaltic pumphead, with the flow from the twin tubes directed to a single tube by a Y-connector.
While pumps embodying these approaches may adequately address the problem of reduction of flow pulsation, they are not capable of providing synchronized flow through all of their parallel flow conduits. In the pump of U.S. Pat. No. 4,834,630, flow through fluid conduits associated with one of the two rotor segments is not synchronous with flow through the other rotor segment. Thus, to employ this pump in an application requiring synchronous flow through a large number of fluid conduits, the number of independent flow conduits would be limited to one-half of the number of conduits which the pump is designed to accommodate.
A general object of the invention is to provide a peristaltic cartridge pump which has greater versatility than the above-described pumps with respect to providing precisely controlled output flow meeting criteria associated with specific laboratory applications or other applications.